1. Technical Field
The present invention relates to a binder resin for an electrostatic image developing toner, a binder resin particle liquid dispersion for an electrostatic image developing toner, a production method of an electrostatic image developing toner, an electrostatic image developing toner, an electrostatic image developer, an image forming method and an image forming apparatus.
2. Related Art
With rapid spread of digitization technology, high image quality is recently demanded in the output such as print and copy in the office or publishing field. Meanwhile, demands for low energy and energy saving in corporate activities and activity result products are increasing so as to realize a sustainable society. To keep up with this trend, also in the image forming method by an electrophotographic process, electrostatic recording process or the like, it becomes necessary to save the electric power in the fixing step involving a large energy consumption or realize implementation of an activity with a low environmental load in the step of producing a product by using the material obtained. The countermeasure for the former includes more reduction in the toner fixing temperature. When the toner fixing temperature is lowered, in addition to power saving, the waiting time until the fixing member surface reaches the fixing possible temperature after turning on the power source, so-called warm-up time, can be shortened and the life of the fixing member can be prolonged.
As for the binder resin of a toner, a vinyl-based polymer has been heretofore widely used, but a vinyl-based polymer having a high molecular weight has a high softening temperature and the heat roller must be set to a high temperature so as to obtain a fixed image with excellent glossiness, which runs against energy saving.
On the other hand, a polyester resin has a rigid aromatic ring in the ring and in turn is flexible as compared with the vinyl-based polymer, and this enables setting low the molecular weight when the mechanical strength is the same. Also, design as a low-temperature fixing resin is advantageously easy in view of intertwining of molecular chains, limit molecular weight and the like. Therefore, polyester is being used as the binder resin for an energy-saving toner in many cases.
The polycondensation of a polyester usually requires a reaction for a long time of 10 hours or more at a high temperature exceeding 200° C. under highly reduced pressure with stirring by a large force and incurs massive energy consumption. In addition, a huge equipment investment is often required for obtaining durability of the reaction equipment.
As for the polyester binder resin, a noncrystalline polyester resin obtained by polycondensing mainly an aromatic polyvalent carboxylic acid (e.g., terephthalic acid, isophthalic acid), an aliphatic unsaturated carboxylic acid (e.g., fumaric acid, maleic acid), a diol having a bisphenol structure, and an alicyclic dial (e.g., aliphatic diol, cyclohexanedimethanol) has been heretofore used.